The present invention relates to weighing scales, and in particular to top-pan scales comprising a scale pan supported on a force transducer and having a corner load sensor for measuring tilting of the scale pan relative to the force transducer. The invention also relates to methods for measuring tilting of a scale pan relative to a force transducer which supports the scale pan, caused by corner loads in a top-pan scale.
Publication DE 30 03 862 A1, which is hereby incorporated by reference into the present application, discloses an electronic scale comprising a scale pan and parallel guidance for the load pan. In order to reduce corner load errors, the parallel guidance has adjusting elements which are provided only for coarse adjustment. At least one sensor is provided, which measures the torques transmitted from the load pan to the parallel guidance, with which torques the weight value output by the scale can be corrected.
Reference DE 299 18 562 U1, which is hereby incorporated by reference into the present application, discloses a scale with a scale pan for placing the goods being weighed and having a force measuring cell which supports the scale pan. The scale has means for providing the common center of gravity of the goods being weighed together with the scale pan in the force measuring direction of the force measuring cell. For this purpose, at least two force measuring cells are arranged on the scale pan one above the other and spaced apart from the axis of the force measuring direction.
Publication DE 38 11 942 A1, which is hereby incorporated by reference into the present application, discloses an electronic scale including a corner load sensor. The scale has a scale pan which is supported above a lower pan on a load transducer. Using the corner load sensor, the torques transmitted from the scale pan to the load transducer can be measured. The lower pan is configured to be elastically flexible, wherein at least three distance sensors which measure the bending of the lower pan dependent on the size of the load and the position of the load on the scale pan are provided on the force transducer. As distance sensors, for example, eddy current sensors or optical distance sensors are proposed. However, the accuracy achievable with distance sensors of this type is not sufficient for many applications.
Patent DE 195 02 694 C1, which is hereby incorporated by reference into the present application, discloses an electronic scale having a load transducer and a capacitive corner load sensor. The corner load sensor serves to measure the torque acting on the load transducer and includes at least three horizontal electrodes and a horizontal counter-electrode, wherein either the electrodes or the counter-electrode are fastened to the load transducer. When a corner load acts, the capacitances formed between the electrodes and the counter-electrodes are changed. Evaluation of these changes permits conclusions to be drawn concerning corner loads that are present. The accuracy achievable with this solution is also not sufficient for many applications.
Reference DE 10 2006 031 950 B3, which is hereby incorporated by reference into the present application, discloses a top-pan scale having a scale pan and a corner load sensor. The scale pan is supported on at least one force transducer of a force measuring system. The corner load sensor emits a signal as soon as the goods being weighed on the scale pan are in an off-center position. The corner load sensor has a planar underside with which the sensor is fastened to the scale pan or a lower pan of the scale. The corner load sensor also has a planar upper side onto which the scale pan is placed. The corner load sensor is linked via a force-transfer-free connection to a correction electronic system of fixed location. The force-transfer-free connection can be implemented with a radio link or an optical link. Using this solution, electric conductors which run to the corner load sensor and could therefore falsify the measurement result are avoided. However, this solution requires a high level of outlay to provide the force-transfer-free connection.